Pluto Probe’s Jupiter Flyby Found Moon, Planetary Surprises

NASA’s New Horizons probe, on its way to a rendezvous with Pluto, spent several months earlier this year observing Jupiter while using the big planet’s gravitational field to sling itself into the outer solar system.

Some of the stunning views snapped by the probe were released earlier in the year, along with descriptions of powerful volcanic activity on the moon Io, tiny moons in the planet’s rings, and new information on the Little Red Spot, three powerful storms that have merged over the past 10 years, that now cover a territory about 70 percent as broad as the diameter of the earth.

Now this week, scientists are presenting detailed reports on their findings at an American Astronomical Society meeting in Florida, along with a special section on their work to be published in the Oct. 12 issueofScience.

Researchers say New Horizons was able to gain particularly detailed observations of Jovian weather, registering massive clouds of ammonia developing in the lower atmosphere, and watching heat-induced lightning strikes in the polar regions. This was the first polar lightning ever observed off of Earth, and showed that heat can move through water clouds virtually everywhere across Jupiter’s surface.

The Little Red Spot, one of the most significant features to emerge on the planet’s surface in the last decade, was observed to be both smaller, and to have higher winds than during the Galileo orbiter’s passage in 1997, with winds now comparable to those in the Great Red Spot.

The probe’s instruments let scientists make detailed size and speed measurements of "waves" of storm energy that ripple across the planet’s surface. Separately, they discovered plasma "blobs" drifting down the planet’s magnetotail (the region affected by the planet’s magnetic field, but distorted by the flow of the solar wind), as well as unexpected atmospheric material flowing away from the surface into space.

"It’s clear there’s significant escape of material from the planet because the brightest burst we see turns out to be material that’s largely from Jupiter, not from the solar wind or Io," said Southwest
Research Institutes’s David McComas, principal investigator for the probe’s Solar Wind Around Pluto (SWAP) instrument.

Off the surface itself, researchers spotted 11 different volcanic plumes on the moon Io, along with infrared glow from at least 36 volcanoes. They measured lava temperatures up to 1900 degrees Fahrenheit, similar to volcanoes on Earth. The resulting map of Io’s surface shows considerable change since Galileo’s flyby in 2001, cementing the moon’s status as the solar system’s most geologically active body, scientists said.

New Horizons will reach Pluto in July 2015, and then head deep into the
Kuiper belt of icy, rocky objects that forms the outer reaches of the solar system.